Research On Regularities And Risk Of The Landslides Distribution Of Xinlong Small Watershed In Luding County

Xinlong watershed, whose drainage area is 89.3 km2, is 26 kilometers south away from LuDing County. It is a region with complicated geological conditions where the geological hazards are frequent. The frequently occurrence of landslide hazard does harm to the life and property of the residents living in the small watershed.This paper regards Xinlong small watershed as the study area to study the 29 landslides developed from May 2008 to March 2014. It calculates quantity contribution rate, area contribution rate and comprehensive contribution rate of different parameters to find the regularities of distribution of the landslides in the study area by reference to the basic geological data completed by predecessors and gathering the statistics of slope angle, slope orientation, elevation, stratum and distribution of precipitation of the landslides:(1)Calculate quantity contribution rate, area contribution rate and comprehensive contribution rate of different slope angles. According to different contribution rates, the slope angles can be divided into three categories (low/medium/high) to find the slope angle with highest contribution degree of landslide development in Xinlong small watershed.(2)Calculate quantity contribution rate, area contribution rate and comprehensive contribution rate of different slope orientations. The number and area of south-facing adrets (90-270 degrees) and north-facing ubacs (270-90 degrees) of landslides are counted to find the difference between the two. Further search for the slope orientation range of which higher contribution degree to landslide development from adrets according to comprehensive contribution rate of slope orientation.(3)Calculate quantity contribution rate, area contribution rate and comprehensive contribution rate of different elevations. Compare the quantity contribution rate of different elevations and the area contribution rate of different ones, observe the difference of the two and make an explanation that combines with the influence of human engineering activities in the study area. Search for preponderant elevation range by comprehensive contribution rate and comparing contribution rate of high contribution degree with one of medium to evaluate the relationship between the regularities of distribution of the landslides and the human engineering activities in the study area.(4)Calculate quantity contribution rate, area contribution rate and comprehensive contribution rate of different stratums. Compare lithology characters of different stratums, then consider the consistency of the quantity, area and comprehensive contribution rate of different stratums according to the characters, which is to search for the stratums of high contribution degree of landslide development in the study area. Further calculate the average area of landslides in different stratums which is compared with lithology to observe consistency with the regularity of distribution of the landslides.(5)Calculate quantity contribution rate, area contribution rate and comprehensive contribution rate of different distributions of precipitation. Confirm the annual precipitation range of high contribution rate of landslide development according to comprehensive contribution rate of annual precipitation in the study area, then observe the consistency of the regularity of annual precipitation distribution and general rule. If both of the above are inconsistent, consider the influence of integrated factors on landslide development, including slope angle, slope orientation, elevation and stratum。Based on the research of the regularities of distribution, further make an assignment of contribution degree for all parameters in order to quantitatively evaluate the risk of the landslides in the study area. Consequently, judge the possibility of landslide reactivation in the study area and the upper and lower possibility of the occurrence of landslide which dates from a slope preliminary.Finally draw a conclusion of the risk of Heigoutou landslide which is the typical landslide recently raised in the study area, by the sum of contribution assignment of the landslide parameters. Make numerical simulation analysis of its stability by FLAC3D which is a numerical simulation software, through the comparison with the practical phenomena, to validate the correctness of the landslide risk which is judged by the regularities of distribution of the landslides in the study area.